The three-dimensional (3D) open boundary eddy current field induced by heavy current flowing in the coils and winding leads in large power transformers is calculated. The eddy current loss and local overheating problem in the tank wall and in the ascending flange of bushings are analyzed and reported in this paper. The effectiveness of a magnetic by-pass plate near the coil ends for reducing the eddy current loss and local overheating in the clamp plates is discussed.

No abstract